Medical implants may provide, for example, unobstructed conduits through a blood vessel in the area of a stenosis. An implant may also be used to treat a vascular aneurysm, for example, by removing pressure on a weakened part of an artery so as to reduce the risk of rupture. A variety of medical devices have been provided with barbs which engage a lumen wall in which the device is implanted and which assist in resisting migratory movement of the device. Such implants are commonly adapted for endoluminal delivery to the deployment site.
The use of shape-memory materials in medical applications is well known. Shape memory materials are materials which can undergo a reversible change from a first “remembered” shape to a second shape.
Nitinol nickel-titanium alloys and doped nickel-titanium alloys (hereafter referred to collectively as Nitinol) are well known as shape memory materials which are used in many medial devices. Nitinol, when heat treated in accordance with known techniques, attains a first “remembered” shape in which it is in an austenitic state. In that state, the material is elastic or super elastic. Nitinol can undergo a reversible phase change, however, from the austentitic state to the martensitic state, in which it is pliable (like cooked spaghetti) and inelastic. This change may be temperature induced or stress induced.